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Urgent - Comet Lucas Dynamo doesn't appear to be charging

ah_sprite

Forum Website User
VOC Member
Hi all
I've been using my bike for the past few months but have rarely needed to use the headlight etc. I'm supposed to be heading away for the weekend on the bike, but having gone out for a test ride at dusk this evening, I'm not so sure I'm going to be, now.

My 52 Comet has been converted to 12v, and is running a Lucas dynamo (all done by a previous owner).
When testing the voltage across the battery when running, I can't get it to read anything above 12v or so.

Can anyone tell me what conversion this bike has? I've attached a couple of (horrendous) photos to show what's inside the old Lucas regulator box. I've taken the end off the dynamo - the brushes seem to be OK and there's nothing obvious untoward.

Any suggestions for diagnosing the issue? Would much appreciate all the help I can get! I'm much more used to restoring 50s and 60s British sports cars, and not entirely sure how the charging system relates to that on this particular bike!






Regards
Richard
 

b'knighted

Well Known and Active Forum Website User
VOC Member
Hi Richard,

Your problem is the urgency. Sorting you out by remote control in a day is probably impossible.
If you are running a magneto a weekend away only uses needs better charging if you are riding more in the dark.
Are you going alone or with another rider with whom you can swap and reswap batteries?
Can you carry a spare battery to replace yours if it goes flat?
If you disconnect the battery does the charging system put out a better voltage? Make sure all the lights are off as an increased voltage can damage bulbs. If so it may suggest that your battery is the problem.

Longer term, if you have an antique charging system replace all bulbs with LEDs. Even if you decide to keep an incandescant headlamp bulb you will reduce the draw of all the other bulbs on the system.
I am setting up an entirely LED system on a bike with no charging system – its fag packet sized Li-ion batterywill run the LED headlamp and rear lamp for more than eight hours. The LED headlamp bulbs ( http://www.ebay.co.uk/itm/2-Pcs-H7-...arts_Vehicles_CarParts_SM&hash=item3f37327966 ) do not produce a very focussed beam so probably wouldn't pass an MoT but they will let you see where you are going. The main will probably dazzle oncoming traffic and the dip does not throw out enough light for riding at any speed. I already have this lighting system on a Comet with a low wattage Miller dynamo and vReg II solid state regulator. It uses a small gel battery in a period rubber body. I live in an area with no street lights but because of the way the lanes tunnel through the trees I use lamps in daylight.
 

Chris Launders

Well Known and Active Forum Website User
VOC Member
Hi Richard
The first thing to do is clean the commutator with some fine wet and dry as you haven,t used the lights this may have become glazed. this used to happen to one of my bikes about every 300 miles, eventually cured with getting brushes from a dynamo specialist as the cheap buy anywhere ones could be the wrong grade of carbon. Google MATCHLESS CLUELESS a site by a matchless owner with a guide showing you all you will need to know, try and do as well as many improvements.
Chris.
 

nkt267

Well Known and Active Forum Website User
VOC Member
If you disconnect the battery with any of the electronic regulators that I have tried then you get NO output..A lot of these regulators need at least 3 to 4 volts to trigger them..Flat battery----No volts..
Are you getting any lights?...Do your lights get brighter when you rev the engine? have you tried to see what the voltage across the battery is with the lights turned on,you could have a duff battery.
A battery with vitrually no capacity will still show 12 volts till you put a load on it..John
 

Matty

Well Known and Active Forum Website User
VOC Member
Hi

If you are going fairly slowly on a system with a 6volt dynamo with a 12volt regulator then it will not produce enough output to run the headlight at much below 45 mph. A 6Volt dynamo will work with a 12 volt system but is not ideal because the field winding has to work harder and more revs are needed to get the required output. However some people do go for the best but expensive solution of having a 12v armature and field fitted but you will be lucky if this is the case.

First check the dynamo on its own by pulling out the connector to the battery/ampmeter from the dynamo(usually marked D ) and if fitted the connection to the field winding (usually marked F). Sometimes there is a two pin connection but with conversions the field is sometimes taken directly from inside the dynamo casing to the regulator - often coloured green.

Then connect a voltmeter between D and the frame/engine and run the engine say up to 2000 revs. You should read the voltage produced by the dynamo from residual magnetism and it should be around 1.5 volts DC.

Next connect the field (F) to D so that this voltage is fed from the dynamo to the field and run the engine again - if the dynamo is OK you should get quite a high voltage (say15/20 volts) at the D/F junction depending on engine revs.

If this is OK then the dynamo is probably in good shape and the fault is the regulator, the wiring or the battery.

Some electronic regulators will not produce output if the battery is flat and in any case perform poorly at low engine revs. I have found that the regulator made by Dynamo Regulators works from a flat battery and gives better output at lower revs. I would like to point out that I have no commercial axe to grind with them however but just found them good to deal with and having a great product.

Matty
 

BigEd

Well Known and Active Forum Website User
VOC Member
VOC Forum Website Moderator
Hi
Some electronic regulators will not produce output if the battery is flat and in any case perform poorly at low engine revs. I have found that the regulator made by Dynamo Regulators works from a flat battery and gives better output at lower revs.

Matty
A friend had poorly functioning electronic regulator supplied by a company that supplies a large variety of components for motorcycles. After complaining a replacement was supplied. This didn't work satisfactorily either. (Why do suppliers keep sending out things they know are inadequate or just no good? Answer = £££ $$$.)
He has now purchased a unit from Dynamo Regulators and this works perfectly.
 

vibrac

Well Known and Active Forum Website User
VOC Member
the words ," Lucas" and "dynamo" should not be associated with "urgent" unless its the late lamented rock group.
I am sure if there was anything better back in the fifties PCV would have fitted it. Unfortunately the accessory market was jumping to the demands of BSA and AMC, " use the cheapest we can get away with" was always their motto in accessories and plant and machinery.
 

Matty

Well Known and Active Forum Website User
VOC Member
Hi
My Miller dynamo has been excellent for the last 58 years though I have made it look like a Lucas one in order to use a modern electronic regulator.

As a retired professional electrical/electronic engineer I help to fix many of the electrical problems for my branch of the VMCC and find that both the Miller and Lucas Dynamos work very reliably PROVIDED the owners keep oil out, check and renew the brushes regularly, check the commutator is clean and renew the bearings as necessary.

I usually replace bearings with sealed ones, which after all work for years in car alternators.

If anybody wants to know how to convert a Miller dynamo to look electrically like a Lucas one using a DYNAMO REGULATOR regulator I have produced a set of instructions which I have attempted to attach as a JPEG picture file, but this system refuses to accept it for some reason.

Any ideas how I can load this 400K jpeg file into the system please ?

The Dynamo Regulator site also has good instructions on how to do this and is another slant on the same theme.
 

BigEd

Well Known and Active Forum Website User
VOC Member
VOC Forum Website Moderator
Any ideas how I can load this 400K jpeg file into the system please ?
Dear Matty,
  1. Start a new message or click "Reply" for an existing message.
  2. Open the window where your image file is store.
  3. Drag the image file onto your message.
  4. The file will upload. It may take a little while depending on the size of the file, speed of connection, etc.
  5. When uploaded you should find a "thumbnail" of your image at the bottom of the message.
  6. A button near the "thumbnail" gives the option to view the image full size.
I just tried this with a 971 Kb image and it worked fine.
 
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